1,721,189 research outputs found
SN1-XFEXOY - A NEW MATERIAL WITH HIGH-CARBON MONOXIDE SENSITIVITY
No full textThe preparation method and the sensing properties (sensitivity and selectivity to interfering gases) towards carbon monoxide of the new ternary compound Sn1-xFexOy, deposited in the form of thin films, are presented in this paper. The metal of the VIIIB group is introduced with concentrations in the range 0<x<25 at. %. Thin films are sputtered using the RGTO (rheotaxial growth and thermal oxidation) technique. This technique consists of metal deposition onto a substrate maintained at a temperature higher than the metal melting point and metal oxidation by means of an annealing cycle in pure oxygen. Particular emphasis is given to the relations between some preparation parameters of the material, namely the atomic percentage of iron or the annealing cycle, and to the sensor sensitivity towards CO and other interfering gases like C2H5OH, H-2 and NOx diluted in dry air. A sensitivity S=(C-gas-G(air))/G(air)=3.5 towards 10 ppm of CO has been measured: the kinetic characteristics of the sensors are also presented, together with the working mechanism
Physical vapor deposition of copper oxide nanowires
No full textCopper oxide nanowires have been successfully prepared by vapor phase transport technique. The deposition conditions strongly influence the morphology of the nanostructures and in turn their electrical and functional properties. Micro-structural investigation and analysis of the electrical properties were performed together with electrical and functional characterization. Transmission electron microscopy confirmed the high crystalline properties and elemental composition of copper oxide nanostructure. P-type semiconductor and sensing behavior has been proved
Resurgence and 1/N Expansion in Integrable Field Theories
Full text linkIn theories with renormalons the perturbative series is factorially divergent even after restricting to a given order in 1/N, making the 1/N expansion a natural testing ground for the theory of resurgence. We study in detail the interplay between resurgent properties and the 1/N expansion in various integrable field theories with renormalons. We focus on the free energy in the presence of a chemical potential coupled to a conserved charge, which can be computed exactly with the thermodynamic Bethe ansatz (TBA). In some examples, like the first 1/N correction to the free energy in the non-linear sigma model, the terms in the 1/N expansion can be fully decoded in terms of a resurgent trans-series in the coupling constant. In the principal chiral field we find a new, explicit solution for the large N free energy which can be written as the median resummation of a trans-series with infinitely many, analytically computable IR renormalon corrections. However, in other examples, like the Gross-Neveu model, each term in the 1/N expansion includes non-perturbative corrections which can not be predicted by a resurgent analysis of the corresponding perturbative series. We also study the properties of the series in 1/N. In the Gross-Neveu model, where this is convergent, we analytically continue the series beyond its radius of convergence and show how the continuation matches with known dualities with sine-Gordon theories
Growth of large-grain CuInSe2 thin films by flash-evaporation and sputtering
No full textThin films of (112) oriented CuInSe2, with an average grain size larger than 50 μm, have been grown by flash-evaporation and sputtering. Platelets of Corning glass 7059, 1 inch2 in size, covered by a layer of lead 2 μm thick, have been used as substrates. The lead layer is prepared by a new method which allows one to obtain (111) oriented films with a grain size ranging between 30 and 500 μm. This method is now being patented. Solar cells using CuInSe2/CdS thin films, prepared by flash-evaporating low resistivity CdS thin films on top of CuInSe2, have so far exhibited high photocurrents close to 40 mA cm-2 at 100 mW cm-2 solar illumination, and a maximum efficiency of about 4%
Growth kinetics of CdSe quantum dots generated in polar polymers
No full textGrowth kinetics of CdSe nanocrystals generated inside three selected polymers (polyvinylpyrrolidone - PVP, polyethyleneglycol - PEG and polyvinylalcohol - PVA) are demonstrated to follow a self-catalytic path, with growth rates depending on the nature of the polymer, i.e. on the capability to activate the cadmium species present in the solution of a metal precursor. A two-step process drives the size evolution of nanocrystals and a critical diameter value can be identified at which the growth regime changes. The medium-term stability evaluation of nanocomposites indicates that, after an initial rearrangement, polymers keep stable the embedded CdSe nanocrystals
Large grain (112) oriented CuInSe2 thin films grown by R.F. sputtering
No full text(112) oriented CuInSe2 thin films with grain size larger than 30 microns have been grown by magnetron RF sputtering on a glass substrate covered by a crystalline thin metalic layer obtained by a novel method. The CuInSe2 targets have been prepared by melting Cu, In, and Se in a high-pressure furnace using B2O3 as an encapsulant. The structural and electro-optical properties of CuInSe2 films have been found to depend on substrate temperature, sputtering power, substrate bias, target stoichiometry, and deposition rate. CuInSe2/CdS solar cells prepared by flash-evaporating CdS on top of RF-sputtered CuInSe2 films have so far exhibited high photocurrents, close to 40 mA/cm2 at 100-mW/cm2 illumination, and a maximum efficiency close to 4 percent
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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